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Given that x^4 – 25x^2 = 144, which of the following is NOT
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Updated on: 03 May 2013, 03:14
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Given that x^4 – 25x^2 = 144, which of the following is NOT a sum of two possible values of x? A. 7 B. 1 C. 0 D. 3 E. 7
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Originally posted by subhashghosh on 30 Jan 2011, 04:38.
Last edited by Bunuel on 03 May 2013, 03:14, edited 2 times in total.
Edited the question



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Re: MGMAT Challenge question doubt
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30 Jan 2011, 06:23
subhashghosh wrote: Hi
I have a doubt in this question :
Given that x^4  25x^2 = 144 , which of the following is NOT a sum of two possible values of x ?
Official Answer  D
The roots are x = 4 or 4, and 3 or +3
These values are considered for the sum,
7 = 4+ 3
1 = 4 + 3
0 = 4 + 4 or 3 + 3
7 = 4 + 3
But why was 4 3 not considered ?
Regards, Subhash Subhash, please read and follow: howtoimprovetheforumsearchfunctionforothers99451.html So please: Provide answer choices for PS questions.Original question is: Given that x^4 – 25x^2 = 144, which of the following is NOT a sum of two possible values of x? A. 7 B. 1 C. 0 D. 3 E. 7 Factor \(x^425x^2+144=0\) > \((x^2  16)*(x^2  9)=0\) > \(x^2=16\) or \(x^2=9\) (alternately you could solve \(x^425x^2+144=0\) for \(x^2\) to get the same values for it) > \(x=4\) or \(x=4\) or \(x=3\) or \(x=3\). All but option D. could be expressed as the sum of two roots: A. 7=43; B. 1=3+4; C. 0=33 (or 0=44); E. 7=3+4. Answer: D. As for your question: there are no enough answer choices to show all possible values of a sum of two roots, so there are 4 possible values for a sum and one which is not. Hope it's clear.
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Re: MGMAT Challenge question doubt
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01 May 2013, 05:07
Bunuel wrote: subhashghosh wrote: Hi
I have a doubt in this question :
Given that x^4  25x^2 = 144 , which of the following is NOT a sum of two possible values of x ?
Official Answer  D
The roots are x = 4 or 4, and 3 or +3
These values are considered for the sum,
7 = 4+ 3
1 = 4 + 3
0 = 4 + 4 or 3 + 3
7 = 4 + 3
But why was 4 3 not considered ?
Regards, Subhash Subhash, please read and follow: howtoimprovetheforumsearchfunctionforothers99451.html So please: Provide answer choices for PS questions.Original question is: Given that x^4 – 25x^2 = 144, which of the following is NOT a sum of two possible values of x? A. 7 B. 1 C. 0 D. 3 E. 7 Factor \(x^425x^2+144=0\) > \((x^2  16)*(x^2  9)=0\) > \(x^2=16\) or \(x^2=9\) (alternately you could solve \(x^425x^2+144=0\) for \(x^2\) to get the same values for it) > \(x=4\) or \(x=4\) or \(x=3\) or \(x=3\). All but option D. could be expressed as the sum of two roots: A. 7=43; B. 1=3+4; C. 0=33 (or 0=44); E. 7=3+4. Answer: D. As for your question: there are no enough answer choices to show all possible values of a sum of two roots, so there are 4 possible values for a sum and one which is not. Hope it's clear. How did u calculate the highlighted part.



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Re: MGMAT Challenge question doubt
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01 May 2013, 05:20
Rajkiranmareedu wrote: Bunuel wrote: subhashghosh wrote: Hi
I have a doubt in this question :
Given that x^4  25x^2 = 144 , which of the following is NOT a sum of two possible values of x ?
Official Answer  D
The roots are x = 4 or 4, and 3 or +3
These values are considered for the sum,
7 = 4+ 3
1 = 4 + 3
0 = 4 + 4 or 3 + 3
7 = 4 + 3
But why was 4 3 not considered ?
Regards, Subhash Subhash, please read and follow: howtoimprovetheforumsearchfunctionforothers99451.html So please: Provide answer choices for PS questions.Original question is: Given that x^4 – 25x^2 = 144, which of the following is NOT a sum of two possible values of x? A. 7 B. 1 C. 0 D. 3 E. 7 Factor \(x^425x^2+144=0\) > \((x^2  16)*(x^2  9)=0\) > \(x^2=16\) or \(x^2=9\) (alternately you could solve \(x^425x^2+144=0\) for \(x^2\) to get the same values for it) > \(x=4\) or \(x=4\) or \(x=3\) or \(x=3\). All but option D. could be expressed as the sum of two roots: A. 7=43; B. 1=3+4; C. 0=33 (or 0=44); E. 7=3+4. Answer: D. As for your question: there are no enough answer choices to show all possible values of a sum of two roots, so there are 4 possible values for a sum and one which is not. Hope it's clear. How did u calculate the highlighted part. Solving and Factoring Quadratics: http://www.purplemath.com/modules/solvquad.htmhttp://www.purplemath.com/modules/factquad.htmHope it helps.
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Re: MGMAT Challenge question doubt
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03 May 2013, 01:38
Rajkiranmareedu wrote: Bunuel wrote: subhashghosh wrote: Hi
I have a doubt in this question :
Given that x^4  25x^2 = 144 , which of the following is NOT a sum of two possible values of x ?
Official Answer  D
The roots are x = 4 or 4, and 3 or +3
These values are considered for the sum,
7 = 4+ 3
1 = 4 + 3
0 = 4 + 4 or 3 + 3
7 = 4 + 3
But why was 4 3 not considered ?
Regards, Subhash Subhash, please read and follow: howtoimprovetheforumsearchfunctionforothers99451.html So please: Provide answer choices for PS questions.Original question is: Given that x^4 – 25x^2 = 144, which of the following is NOT a sum of two possible values of x? A. 7 B. 1 C. 0 D. 3 E. 7 Factor \(x^425x^2+144=0\) > \((x^2  16)*(x^2  9)=0\) > \(x^2=16\) or \(x^2=9\) (alternately you could solve \(x^425x^2+144=0\) for \(x^2\) to get the same values for it) > \(x=4\) or \(x=4\) or \(x=3\) or \(x=3\). All but option D. could be expressed as the sum of two roots: A. 7=43; B. 1=3+4; C. 0=33 (or 0=44); E. 7=3+4. Answer: D. As for your question: there are no enough answer choices to show all possible values of a sum of two roots, so there are 4 possible values for a sum and one which is not. Hope it's clear. How did u calculate the highlighted part. To calculate the roots of a quadratic equation ax^2+bx+c=0 you can use the formula roots =(b +sqrt(b^24ac))/2a...and .....(b sqrt(b^24ac))/2a now in this x^425x^2+144=0===>just for convenience put x^2= X therefore equation becomes: X^225X+144=0 NOW using the formula of roots X=(25+sqrt(25^24*1*144))/2 and X=(25sqrt(25^24*1*144))/2 On simplifying X=16...AND X=9 now replacing back X WITH x we get x^2=16 and x^2=9 therefore four roots are x=+4,4,+3,3 hope it helps... SKM hope it h
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Re: Given that x^4 – 25x^2 = 144, which of the following is NOT
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03 Jul 2013, 01:23
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Re: Given that x^4 – 25x^2 = 144, which of the following is NOT
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03 Jul 2013, 10:19
subhashghosh wrote: Given that x^4 – 25x^2 = 144, which of the following is NOT a sum of two possible values of x?
A. 7 B. 1 C. 0 D. 3 E. 7 Factorization of roots initially conisder 144 and now diivide this to roots which add to 25 => 16, 9 and now x^2 9 and x^2 15 one of them is equal to zero, equate and we get l3l l4l as the roots so add them individually in all combniations we can achieve all othe but not 3 as sum of two roots so the answer is D hope this helps



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Re: Given that x^4 – 25x^2 = 144, which of the following is NOT
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03 Jul 2013, 13:50
Assume, \(x ^2 = y\); then the equation is \(y^2 25y+144=0\) sum of the roots = 25 = y1 + y2 product of the roots = \(144 = y1 * y2\) ==> y1  y2 = 7 ==> y1 = 16 and y2 = 9 ==> \(x^2\) = 16, 9 ==> x = +4, 4, +3 , 3 so sum of any two values of x is not '3'
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Re: Given that x^4 – 25x^2 = 144, which of the following is NOT
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17 Oct 2019, 01:01
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Re: Given that x^4 – 25x^2 = 144, which of the following is NOT
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